1. Field of the Invention
The present general inventive concept relates generally to a method of generating a power to supply to elements in a power supply apparatus. More particularly, the present general inventive concept relates to a method of generating a power to drive elements at a primary side of a power supply apparatus.
2. Description of the Related Art
A liquid crystal display (LCD) applies electro-optic effects of a liquid crystal to a display device. The liquid crystal is between a liquid state and a solid state and flows having the characteristics of both a liquid and a solid. The LCD is used as a monitor, a digital television, and other display devices. Hereinafter, a power supply apparatus to drive an LCD is described with reference to FIG. 1.
FIG. 1 illustrates a conventional power supply apparatus to drive an LCD back-light (lamp). The power supply apparatus includes an alternating current (AC) input section 100, a rectifier 102, a power factor correction (PFC) section 104, a converter 110, a main board 130, an inverter 120, and a lamp 132. The PFC section 104 includes a PFC 106 and a rectifier 108. The converter 110 includes a switch 112, a transformer 114, and a rectifier 116. The inverter 120 includes a switch 122 and a transformer 124. Operations of the elements of the power supply apparatus for driving the LCD will now be described.
The AC input section 100 receives an AC power supply. An intensity of the AC power may vary depending on a user setting. The rectifier 102 rectifies the AC power received from the AC input section.
The PFC section 104 improves a power factor with respect to the power received from the rectifier 102. Typically, if the power received from the rectifier 102 is used without any power factor processing, power utilization may decrease. Accordingly, the PFC section 104 improves the power factor with respect to the power received from the rectifier 102 in order to enhance the power utilization.
The power output from the PFC section 104 is transferred to the converter 110 and the inverter 120 as a primary power. The switch 112 of the converter 110 repeatedly switches between on and off states to transfer the received primary power (hot) to a secondary side (cold) of the conventional power supply apparatus. Generally, the primary side of the conventional power supply apparatus includes elements up to a primary coil of the transformer 114, and the secondary side includes elements after a secondary coil of the transformer 114. Thus, the secondary side includes the main board 130, the rectifier 116, and the secondary coil of the transformer 114. The primary side includes the lamp 132, the inverter 120 (including the switch 122 and the transformer 124), the switch 112, and the primary coil of the transformer 114.
The transformer 114 transfers the primary power at the primary side to the secondary side depending on whether the switch 112 is in the on or off state. In particular, the transformer 114 generates an induced power in the secondary coil thereof according to whether the switch 112 is in the on or off state and transfers the power induced in the secondary coil to the secondary side. The rectifier 116 then rectifies the power received from the secondary coil of the transformer 114.
The power output from the converter 110 is a secondary power provided to the main board 130. Elements in the main board 130 utilize the secondary power received from the converter 110 as a driving power. The number of secondary output powers received from the converter 110 may vary depending on a user setting or an amount of power required by the elements of the main board 130. That is, the user can vary the amount of secondary power output by the transformer 114 and/or the number of secondary output powers by changing the configuration of the transformer 114.
The primary power output from the PFC section 104 is also transferred to the inverter 120. The inverter 120 inverts the primary power received from the PFC section 104, which is a DC power, to an AC power. The switch 122 and the transformer 124 included in the inverter 120 operate in the same manner as the switch 112 and the transformer 114 included in the converter 110. However, the transformer 114 reduces the amount of the primary power received (i.e., step down) while the transformer 124 increases the amount of the primary power received (i.e., step up). Typically, the power output from the transformer 124 is about 1.8 kV. The power output from the inverter 120 is then provided to the lamp 132. The lamp 132 is driven using the power provided by the inverter 120.
As mentioned above, the elements of the main board 130 are driven using the secondary power received from the converter 110. The elements in the switch 122 of the inverter 120 are driven using the primary power supplied by the PFC section 104. In this situation, the elements of the switch 122 cannot use the power output from the converter 110. Specifically, the power output from the converter 110 is the secondary power, and the elements of the switch 122 are at the primary side of the conventional power supply apparatus. If the elements at the primary side of the conventional power supply apparatus use the secondary power, a short circuit is likely to occur. Accordingly, the elements at the primary side should be driven using the primary power.
FIG. 2 illustrates an apparatus to generate the primary power to be supplied to the elements at the primary side of the conventional power supply apparatus. The primary power to be supplied to the elements at the primary side is derived from the power output from the PFC section 104. The power output from the PFC section 104 is input to a regulator 200. The regulator 200 reduces the input power to a predetermined level and outputs the reduced power. Typically, the power input to the regulator 200 is between 300V and 400V, and the power output from the regulator 200 is about 5V. The power output from the regulator 200 is then supplied to the elements of the switch 122 at the primary side. The elements of the switch 122 at the primary side are driven using the power supplied by the regulator 200.
The difference between the power input to the regulator 200 and the power output from the regulator 200 determines a power loss at the regulator 200. The greater the difference between the input and output power in the regulator 200, the greater the power loss that occurs in the regulator 200. Moreover, since the 300V to 400V power from the PFC section 104 is reduced to 5V by the regulator 200 and is then input to the inverter 120, the transformer 124 is now required to provide a larger increase in power from 5V to about 1.8 kV used to power the lamp 132 (as opposed to between 300V and 400V to about 1.8 kV). Therefore, it would be desirable to reduce the power loss that occurs in the regulator 200 by adjusting the amount of the power input to the regulator 200.